Extruder motor "Thumping" and not pushing enough

My Extruder motor "balks" at anything above a 30 mm per sec printing speed. It is a "Thump, Thump, Thump" sound at about one thump per second, and the head backs up and not enough material comes out. I have a .35mm J-head, and my motor is direct drive 40 N.cm. I am printing with 1.75 ABS at 230C. I tried to slow the travel speed way down in sclic3r and it didn't seem to affect the infill speed at all. I looked thru Marlin Config_H and Adv Config, and had no luck finding anything that might help to limit print speed, did I miss something? Should I expect a faster print speed, and would I be able to demand more speed out of a more powerful extruder motor? Would a better print head allow me to push up the print speed, and keep the high resolution?

Edited 1 time(s). Last edit at 01/22/2014 10:03PM by Nununugent.

Sounds like a extruder stepper motor is binding or having a REALLY hard time moving that filament. What extruder are you using? Check your vref/current being supplied to the motor. 30mm/s with 1.75mm ABS should be nothing. I had a similar issue with the stock Makerbot MK7 extruder. It would 'thump' and not put out enough filament. I replaced the extruder setup with a spring-force ball bearing extruder. Fantastically better now.

Also, just for good measure. Go ahead and back out all of your filament (as if you were changing filaments or had a jam) and cut off a couple inches from that section and feed it in again. Maybe there is a contaminant in there somewhere.

Edited 2 time(s). Last edit at 01/22/2014 11:49PM by MrBaz.